"People like to have them. They draw attention to candidates, that's useful. They can draw money, that's useful to candidates," he said. "But the reality is very few people are voting for one candidate over the other just because a celebrity is supporting them."

He said newspaper endorsements, however, can play a role in some parts of the country.

"The Washington Post has a real impact on mayoral races, on other kinds of races, because their endorsement counts," Mellman said. "People aren't that engaged, aren't that familiar with the candidates, and so when a newspaper that people trust endorses, it makes a difference."

"In other places, people have a very hostile relationship to their local newspaper and that endorsement doesn't necessarily mean a thing," he said.

Mellman's comments come as musician Taylor Swift appears to have contributed to an increase in voter registration after she broke her career-long silence on politics.

“As much as I have in the past and would like to continue voting for women in office, I cannot support Marsha Blackburn,” Swift wrote on Sunday. “I will be voting for Phil Bredesen for Senate and Jim Cooper for House of Representatives.”

Vote.org said it has seen a flood of new voter registrations since Swift's comments.

Polling and public opinion analyst Karlyn Bowman said in an interview that aired Tuesday on Hill.TV that only a tiny number of Republicans would be willing to impeach President Trump over issues like the Russia investigation or obstruction of justice.

Pollster Emily Ekins said in an interview that aired Tuesday on "What America's Thinking" that she was shocked to see that 37 percent Republicans had said in a new Hill-HarrisX poll that they were not opposed to the idea of President Trump pardoning his former associates

Pollster Emily Ekins on Monday told Hill.TV that she doesn't think a large number of Americans necessarily care a lot about the congressional and federal investigations surrounding President Trump and his 2016 campaign, pointing to recent polling on the issue.